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Like in vivo MRS, fMRS can probe different nuclei, such as hydrogen (1 H) and carbon (13 C). The 1 H nucleus is the most sensitive and is most commonly used to measure metabolite concentrations and concentration dynamics, whereas 13 C is best suited for characterizing fluxes and pathways of brain metabolism.
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. [1] [2] This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases. [3]
Resting state fMRI (rs-fMRI or R-fMRI), also referred to as task-independent fMRI or task-free fMRI, is a method of functional magnetic resonance imaging (fMRI) that is used in brain mapping to evaluate regional interactions that occur in a resting or task-negative state, when an explicit task is not being performed.
PET, fMRI, fNIRS and fUS can measure localized changes in cerebral blood flow related to neural activity. These changes are referred to as activations . Regions of the brain which are activated when a subject performs a particular task may play a role in the neural computations which contribute to the behaviour.
Cerebral blood flow (CBF) is the blood supply to the brain in a given period of time. [8] In an adult, CBF is typically 750 millilitres per minute or 15.8 ± 5.7% of the cardiac output. [9] This equates to an average perfusion of 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. [10] [11] [12]
Through a process called the haemodynamic response, blood releases oxygen to active neurons at a greater rate than to inactive neurons. This causes a change of the relative levels of oxyhemoglobin and deoxyhemoglobin (oxygenated or deoxygenated blood) that can be detected on the basis of their differential magnetic susceptibility.
If fMRI can be used to detect the regular flow of blood in a healthy brain, it can also be used to detect the problems with a brain that has undergone degenerative diseases. Functional MRI, using haemodynamic response, can help assess the effects of stroke and other degenerative diseases such as Alzheimer's disease on brain function. Another ...
Functional MRI (fMRI) has been the modality of choice to visualize brain activity, and takes advantages of a range of techniques that can be used to interpret it. However, the signal that fMRI is acquiring is BOLD signal, which does not directly correlate with blood flow.